1. Field of the Invention
This invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that facilitates the repair of defects caused by open or short circuits.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) has a gradually widening range of applications owing to its characteristics such as light weight, a slim profile, low power consumption, etc. Accordingly, the LCD has been used for office automation equipment and video/audio equipment, etc.
Referring to FIG. 1, the conventional LCD includes a source electrode 16 branched from a data line 8 to apply a data signal, and a gate electrode 20 branched from a gate line 14 to apply a scanning signal. The LCD also includes a drain electrode 18 for applying an image signal to a pixel electrode 10. A number of data lines 8 are provided in a vertical direction at a lower glass 2 (shown in FIGS. 2 and 3) to transmit the data signal applied from a data driver (not shown) to each source electrode 16. A number of gate lines 14 are provided in a horizontal direction at the lower glass 2 to be crossed with each data line 8 to transmit a scanning signal applied from a gate driver (not shown) to each gate electrode 20. A scanning signal transmitted from the gate line 14 is applied to the gate electrode 20 to turn on a thin film transistor, thereby transmitting a data signal applied to the source electrode 16 to the drain electrode 18. In other words, the gate electrode 20 switches the data signal in correspondence with the scanning signal. A data signal transmitted to the drain electrode in this manner is applied to the pixel electrode 10, and an orientation of the liquid crystal is changed to correspond with a level of a data signal applied between the pixel electrode 10 and the common voltage layer (not shown).
In this case, since the pixel electrode 10 is a region through which a light beam is transmitted, the larger the pixel electrode area, the higher the aperture ratio of the pixel. Accordingly, as shown in FIG. 1, the pixel electrode 10 is overlapped with the gate line 14 and the data line 8 so as to implement a liquid crystal display device with a high aperture ratio. To this end, an organic protective film with a relatively low dielectric constant of about 2.7 such as Benzocyclobutene (BCB) is used. In this case, since a dielectric constant of the organic protective film is low, it becomes possible to overlap the pixel electrode with the data line. A liquid crystal display device with a high aperture ratio can be implemented by overlapping the pixel electrode with the data electrode in this manner.
A structure of the data line 8 taken along II-II′ line in FIG. 1 will be described in conjunction with FIG. 2. As shown in FIG. 2, a gate insulator (GI) 4 is formed on the upper portion of the lower glass 2. At the upper portion of the GI 4, a semiconductor layer 6 and the data line 8 are sequentially provided. A protective film 12 is coated on the data line 8 and the GI4. The pixel electrode 10 is provided at the upper portion of the protective film 12 so as to overlap with the data line 8 at a desired distance.
Further, a structure of the gate line 14 taken along III-III′ line in FIG. 1 will be described in conjunction with FIG. 3. As shown in FIG. 3, the gate electrode 14 is formed selectively at the upper portion of the lower glass 2. The GI 4 is entirely coated on the gate electrode 14. The protective film 12 is coated on the GI 4. The pixel electrode 10 is provided at the upper portion of the protective film 12 so as to overlap the gate line 14. In order to implement a liquid crystal display device with a high aperture ratio, the gate line 14 and the pixel electrode 10, or the data line 8 and the pixel electrode 10, are overlapped at a desired distance with respect to each other.
In the above-described liquid crystal display device with a high aperture ratio, a distance between the pixel electrodes 10 is narrow enough to generate a short between the adjacent pixel electrodes (e.g., (n,n) and (n+1, n)). Upon generation of the short, a point defect occurs at the corresponding pixels. To cure such a short, a cutting laser is conventionally used. For example, if the (n,n) numbered pixel electrode and the (n+1,n) numbered pixel electrode at the data line 8 is cut along a cutting line 9 (shown in FIG. 1) so as to cut any one of these pixel electrodes when they are shorted together, then the pixel electrode overlapping the gate line 14 must also be cut. In this case, a short circuit is generated between the gate line 14 and the pixel electrode 10 by such cutting. On the other hand, a similar process is performed when the (n,n) numbered pixel electrode and the (n+1,n) numbered pixel electrode at the gate line 14 are shorted, so that a short circuit is generated between the data line 8 and the pixel electrode 10 by such cutting. The conventional liquid crystal display device with a high aperture ratio has a problem in that a successful repair is impossible upon such a short between adjacent pixel electrodes.
FIG. 4 is a plan view of the conventional liquid crystal display device when the data line and the gate line thereof are open. As shown in FIG. 4, an open circuit is generated at the gate line 14 or the data line 8. For example, as shown in FIG. 5, in order to repair an open circuit in the data line 8, the first point P1 and the second point P2 are welded with a separate pattern (or a repairing line) to reform an electric path of the open-circuited data line 8. Similarly, during an open circuit of the gate line 14, an electric path of the open-circuited gate line 14 is reformed in the same manner. As described above, the conventional liquid crystal display device requires a separate pattern or line to repair the open-circuited line. As a result, a new scheme for appropriately repairing an open circuit and a short circuit generated in the liquid crystal display device with a high aperture ratio is required.